Since this phone is a tripleband design, it uses 3 rx filters, connected to the respective Rita inputs:

Epcos B7820 for GSM900

Epcos B7821 for DCS1800

Epcos B7851 for DCS1900

Those are connected to an unknown "T 636 / 5475" antenna switch. The pinout of this switch however is identical with the Panasonic EZFL897TB11C.The control voltage inputs of the switch are connected to the TSPACT outputs of the Calypso DBB through a Fairchild NC7NZ34 triple-buffer.

The idea to use an OsmocomBB-driven phone as an accurate clock source, e.g. for the USRP, by synchronizing the clock to a cell of a commercial operator was discussed on the mailing list a while back. Since the USRP needs an input clock of 52MHz, but the Compal-phones only expose 13 and 26MHz, an external PLL would be required. The DP-L10 however exposes the MCLK/TSPACT11 pin of the Calypso, which is connected through the triple-buffer to the GSM900 TX/Vc3 input of the antenna switch, and thus easily accessible. When the corresponding bit in the MCU_SW_TRACE register is set, this pin outputs the 52MHz clock being fed to the ARM-core, which is phase-locked to the VCTCXO. See the blue circuit path in the picture above.

This is the output captured with a 100MHz scope (and thus limited):

After synchronizing to a cell with the phone, the frequency error measured by the DSP is in the 0-10Hz range.

A nice feature of this phone is that it already has an integrated Silabs CP210x USB-UART, which is supported by Linux. Even faster, odd baudrates of the Calypso DBB are supported by this chip, including the maximum 812.500 baud.Most of the phones seem to use USB vid:pid 0489:e003, which is mainline since Linux 2.6.36 (thus, older kernels need to be patched, the cp210x driver doesn't seem to take the vid/pid via modprobe parameters).

As someone pointed out on the mailing list, you can do the following for Kernels < 2.6.36:

Note: As the power button is not connected to the keyboard scan matrix and can only be read through a Iota status register, which is quite impractical, we use the camera button on the top left side of the phone as a substitute.